In this paper, we present a test of the dynamic trade-off model of capital structure.
We depart from the standard estimation technique of the trade-off model, by directly
estimating a structural model, instead of the standard reduced form equation. Given that
in the structural trade-off model, the target debt-equity ratio is unobservable, the state space
representation is a natural model to test the dynamic trade-off model. We use a
Kalman filter, which allows us to directly estimate the unobserved firm’s target debt equity
ratio.
Under the structural model of the trade-off theory, the firm’s observed, or realized,
debt-equity ratio is a weighted average of last period’s realized debt-equity ratio and the
firm’s target debt-equity ratio. With the estimated model parameters and the estimated
target debt-equity ratio, we suggest a simple test of the trade-off model. This test checks
if the estimated parameters in the structural model foe each firm add up to one
The focus on individual firms allows us to directly study the number of firms in
which the dynamic trade-off model cannot be rejected. In our sample of 578 firms, we
find that the trade-off model holds –i.e., cannot be rejected at the standard 5% level- for
32% when we assume that the target debt-equity ratio follows an AR(1) model. The
model holds for as many as 52% when the target debt-equity ratio is assumed to be
constant. We also estimate the speed of adjustment for each firm. The median and the
average speed of adjustment are .161 and .276, respectively. These numbers are close to
the annual estimates reported in Flannery and Rangan (2006). Confirming Roberts (2002),
we find a huge cross-sectional variation in the speed of adjustment parameter. The
empirical 95% confidence interval for the speed of adjustment has as bounds .025
and .951. The interquartile range, however, is not that extreme, going from .088 to .347.